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Old 03-13-2007, 12:53 PM   #1
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Tires

I need to get some new tires for the Daewoo(Sumitomo HTR200). I've got a knot in one and wear from not being aligned by the previous driver. The OEM were 185/60/14 I'm thinking 175/70/14. Skinner and taller equal better FE? Thoughts?
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Old 03-13-2007, 01:30 PM   #2
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I'm doing the same experiment, but with truck tires. I just changed from 265/75-16to 235/85-16. They're the same diameter.

I was surprised that the truck steers a lot more easily with the new narrow tires. This probably helps reduce load on the power steering pump, in addition to lower rolling resistance and less frontal area.

It seems to upshift earlier now, but it's too soon to give a definitive answer about mileage.
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Old 03-13-2007, 06:51 PM   #3
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Tread Design

I've found that tread design and compound has a large impact on FE (specifically the LRR tire's resistance value). A few tests here have shown that the tire's design (such as tall/skinny) doesn't yield any better economy than traditional, wider designs as the same amount of "contact patch" with the road is present for either design: traditional pumped-up, or do-nut spare (for example).

It seems like it would make sense, as tarmac racing bicycles have tall skinny tires, versus knobby tires for Mountain biking. But there's a lot less weight involved.

Now changing the size for gearing issues is another story, and could essentially change your final ratio. Drag and speed is another concern.

A few threads:

Tire Size

Taller Tires

4 Do-Nuts
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Old 03-13-2007, 07:25 PM   #4
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Thanks,
While researching this I found this:
Proper inflation

With normal street tires on an automobile the contact patch will remain uniform across the tread of the tire. If the tire is over-inflated the tire will tend to bulge in the center of the tread which will lift the edges off the pavement. This can decrease the handling performance of the vehicle and also decrease the life of the tire. Prolonged use of a tire which is over-inflated will cause the tread in the center to wear away faster than the tread on the edges.

An under-inflated tire can have negative effects as well. In this case the center of the tread will not make as much contact with the road surface and the edges of the tread will wear down faster because the sidewalls of the tire will push the edges into the pavement.

One method of checking for proper inflation is to find a long stretch of pavement such as an empty parking lot and then draw a line across the tread with chalk. Then simply drive straight across the parking lot. If the entire line of chalk has rubbed off, the tire is properly inflated. If the center of the line is rubbed off but the ends are still present, the tire is over-inflated. On the other hand, if the line is rubbed off at the ends but is still present in the center of the tread, the tire is under-inflated.

Anybody got a piece of chalk and want to test 35 and 50 psi and see what it does?
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Old 03-13-2007, 07:29 PM   #5
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Quote:
Originally Posted by zpiloto View Post
Thanks,
While researching this I found this:
Proper inflation

With normal street tires on an automobile the contact patch will remain uniform across the tread of the tire. If the tire is over-inflated the tire will tend to bulge in the center of the tread which will lift the edges off the pavement. This can decrease the handling performance of the vehicle and also decrease the life of the tire. Prolonged use of a tire which is over-inflated will cause the tread in the center to wear away faster than the tread on the edges.

An under-inflated tire can have negative effects as well. In this case the center of the tread will not make as much contact with the road surface and the edges of the tread will wear down faster because the sidewalls of the tire will push the edges into the pavement.

One method of checking for proper inflation is to find a long stretch of pavement such as an empty parking lot and then draw a line across the tread with chalk. Then simply drive straight across the parking lot. If the entire line of chalk has rubbed off, the tire is properly inflated. If the center of the line is rubbed off but the ends are still present, the tire is over-inflated. On the other hand, if the line is rubbed off at the ends but is still present in the center of the tread, the tire is under-inflated.

Anybody got a piece of chalk and want to test 35 and 50 psi and see what it does?
Whatever, I don't like my current tires anyway. Too much grip, and too low of a max PSI rating.
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Old 03-14-2007, 01:24 AM   #6
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Ive gotten tires that are wider than the rim, and it made the center of the tread bow outward compared to the sholder of the tread. I would ASSUME a narrower tire would do the oppisite, so you can inflate it more without it wearing unevenly. I looked those up at tirerack.com rated at 51 pounds, and has great user reviews.

The tire presure for the front should be more than the back usally. Especially with front wheel drive. Weight distribution is around 70/30. You just gotta becareful I Had a 2003 Mazda Protege 5 that had Toyo Proxes 4 (spelling...) tires on it that I aired up to rated PSI and they stretched, and handled very ditsy on the ribbed concrete freeways. If they have a mind of thier own you may need to air them down to get more rubber on the ground.
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